Adhesive composition comprising bisthioammeline polyalkylene ether resins



Patented July 21, 1943 zszsm ADHESIVE COMPOSITION COMPRISINGBIS'I'IIIOAHIIELINE POLYALKYLENE s'rmm BESINS Herman A. ilruaon andJames L. Baincy.

Philadelphia, Pa, assi nors to The M- inous Products in ChemicalCompany,

Philadelphia, Pa.

No Application August 15, 1940,

Serial No. 352,137

11 Claims. (cl. zen-s),

This invention deals with improved adhesives based on the condensates ofbisthioammeline polyalkylene ethers and formaldehyde. The preparation ofthese .condensates has been described in application Serial No. 297,280,flied September 30, 1939, now U. S. Patent No. 2,217,667, of which thepresent application represeats a continuation-impart.

It has been found that solutions of the bisthioammeline polyalkyleneether-formaldehyde condensates together with acid-type catalysts areexcellent adhesives and may be used for binding wood, cork, paper,cardboard. cloth, asbestos, sawdust, mineral pigments, animal,vegetable, or synthetic fibers, metal foil. or other substance to thesame or a different material. Condensates of a bisthioammelinepolyallnvlene ether and formaldehyde may be used or condensate of abisthioammeline polyalkylene ether, another methylol-forming compound,such as urea, thicurea, alkyl ureas; phenyl urea, urethane, formamide,acetamide, aryl suifonamides, dicyandiamide, phenol, melamine, etc., andformaldehyde. There may also be used in the solution soluble blood, athickening agent, a filler, or mixtures of these various adJuvants.

As described in the above-identified application a bisthioamme inepolyalkylene ether of the formula II II mN-c c-mn mNc etc., and nrepresents a small integer preferably from one to five inclusive, iscondensed with an aldehyde, particularly formaldehyda'to yield valuablecondensates. Formaldehyde may be used in the form of an aqueous ororganic solvent solution or as a solid polymer. There may also be usedin part as a source of formaldehyde hexamethylene tetramine ordimethyloi urea. Furthermore, there may be used in conjunction withformaldehyde other aldehydes, such as benzaldehyde, acetaldehyde,furfural, etc. The bisthioammeline polyalkyiene ether and formaldehydeand other aldehyde, if used, are best reous formaldehyde is used, theether in powdered form is added to the formaldehyde solution. Itdissolves as it reacts. when the pH of the reaction mixture is aboutneutral, stable condensation products are obtained. Stability andclarity.

of the solution of the condensate are also ensured by addition theretoof a small amount of a lower alcohol. The stability of solutions ofcondensates may also be improved by addition thereto of an alkalineearth salt, particularly calcium chloride, or magnesium chloride, inconcentrations of 2% to 20% based on the weight of thioammeline ether orcombined weight of thioammeline ether or combined weight of thioammellneether and other methylol-forming compound.

The addition and condensation reactions of a bisthioammelinepolyalkylene ether and formaldehyde are performed in a short timebetween and 100 C. under atmospheric pressure. Higher pressures may beused when desired with a shortening of reaction time and without loss offormaldehyde. In general one mol of a bisthioammeline ether reacts withfour to eight mol of formaldehyde, After the initial reaction, excessaldehyde may be removed by addition to the reacting mixture of furtherquantities of a thioammeline ether, or urea, thiourea. dicyandiamide,aniline, a primary or secondary amine, an amide of a monoorpoly-carboxylic acid, sulfonamide, phenol, melamine or other triazine,or other compound which reacts with formaldehyde to form a methylolderivative, so-called methylol-forming compounds. This in effect gives aco-condensate.

Equivalent eilects in forming co-condensates are obtained by mixingbisthioammeline ether, another methylol-forming compound, andformaldehyde at the start of the reaction. Likewise, primary additionproducts or soluble condensates of a bisthioammeline ether andformaldehyde and primary addition products or soluble condensates ofanother methylol-forming compound and an aldehyde may be mixed. Thefinal condensates or resins formed from these mixtures are alsoco-condensates.

The co-condensates which contain at least one part of a bisthioammelineether-formaldehyde reaction product to one part of other resinousmaterials are unusually valuable for their stability, resistance towater, low water absorption, resistance to light, latitude in curingconditions,

"improved ilow under pressure, etc. Yet the ratio may be carried to 1:3with satisfactory results.

For the curing of the condensates based 'on acted in the presence of asolvent. when aqueethers there may be used a wide variety of acid-typecatalysts. Conversion to advanced stages of condensation andpolymerization is accelerated by acids, such as hydrochloric,phosphoric, acetic, formic, lactic, phthalic, maleic, chloroacetic,etc.,'acid salts,'such as methylamine hydrochloride, sodium acidsulfate, etc., potentially acid salts, such as barium ethyl sulfate,ammonium thiocyanate, ammonium chloride, ammonium sulfate, alum, etc.For practical purposes the addition of free acids presents somedifficulties in that there is danger of premature gelatlon and anacidified resin solution must be promptly applied, since it tends to gelvery rapidly. Ammonium salts are highly useful as acidtype catalysts.They become effective apparently because ammonia therefrom is taken upby formaldehyde with the gradual liberation of acid. This sort ofcontrol may be further effected by addition to an acid-type catalyst ofammonia or ammonium hydroxide, which prolongs the spreading life of asolution of one of the bisthioammeline ether-aldehyde adhesives.

It is the preferred practise to add an acid-type catalyst to thesolution of a bisthioammeline ether-aldehyde condensate at the time ofuse or shortly before the time of use of said condensate. When, anadhesive solution is to be used during the course of a day, ammonia inconjunction with the acid-type catalyst prolongs the useful, workinglife thereof.

In the preparation of a mixture for use as an adhesive it is oftendesirable to add thereto one or more thickening agents, that is,materials which themselves thicken a solution of the condensates, suchas a starch, walnut shell flour, or a cereal grain flour, such as rye orwheat flour. These materials may serve one or more purposes. Forexample, thickening agents increase the viscosity of the mix givingimproved spreading properties, lessening penetration or permitting theuse of condensates which in' themselves do not impart sufficientviscosity to solutions but are otherwise satisfactory. These agents alsoreduce the cost of the adhesive composition and allow various economiesin operation. As they increase the time for the spread adhesive todry,they provide more flexible conditions for handling and applyingadhesives.

There may also be used various finely divided extenders, or diluentssuch as diatomaceous earth, alpha-doc, wood-flour, etc. These materialsare believed to act as fillers, increasing the viscosity of the mix, andhelping to compensate for slight irregularities of surfaces. Suchmaterials, however, do not necessarily add strength to the bond.

Another type of material which may be added to solutions of thebisthioammeline-aldehyde condensate is soluble blood. It is known thatblood itself, or blood albumen, has some bonding action but this is lessthan that of the bisthioammelinealdehyde condensates. The addition ofblood, however, to a solution of a bisthioammeline polyalkyleneether-formaldehyde condensate yields an adhesive giving greater strengththan either material alone. Since ulated by heat in the curingoperation, the high water-resistance of the bisthioammeline polyalkyleneether resins is not lessened. Furthermore, the use of blood withco-condensates of formaldehyde, a bisthioammeline polyalkylene ether,and another methylol-forming compound,

particularly the open chain methylol-forming compounds such as urea orthiourea, is advantageous in that the strength and water-resistance frommore economical mixtures are thus rendered blood albumen is coagsimilarto those obtained from the pure bisthioammeline polyalkyleneether-formaldehyde condensates. The bisthioammeline polyalkylene etherformaldehyde condensates and resins effectively prevent the blood orblood albumen from undergoing decay or putrefaction. Blood also has somethickening action on the mixture and thus serves as another type ofthickening agent, increasing the flexibility of conditions in handlingthe adhesive compositions, preventing excessive penetration, etc.

In the application of an adhesive composition comprising a solution of abisthioammeline polyalkylene ether-formaldehyde condensate and anacid-type catalyst for hardening the condensate, the composition isspread over the surface of objects to be bonded. The objects are thenpressed together. Pressures up to several thousand pounds per squareinch may be used. If cold-bonding is to be practised, an eflicientcatalyst'is required and the parts to be Joined are clamped togetheruntil the adhesive is set. The hardening step is much shortened and themaximum water-resistance of the adhesive developed by bonding attemperatures of 200 to 350 F.

Useful adhesive compositions and their preparations are described in thefollowing examples.

Example 1 The following materials were mixed in a reaction vesselequipped with a. stirrer:

Parts p,p'-Bisthioammeline diethyl ether 142 37% formaldehyde in ethylalcohol 191 Ethyl alcohol (denatured) 500 This mixture was heated underreflux for four hours and a clear solution formed with, however,

some resinous material collecting on the walls of the reaction vessel.The solution was filtered and the clear filtrate (570 parts) wasconcentrated to 35% solids content by evaporation.

To parts of this resin solution there was added four parts of a 40%aqueous solution of ammonium thiocyanate. The solution was spread on 9;"birchwood at the rate of 13 grams per square foot of surface to beJoined. Three laminae were assembled and held for five minutes in apress heated with low pressure steam and operated at 200 lbs. per squareinch. This plywood was highly water-resistant by the boiling water test,which failed to delaminate test samples.

A mixture of 100 parts of the above bisthiobisthioammeline ether resinin the adhesive were still intact.

Example 2 One mol of pfl'-bisthioammeline diethyl ether in powdered formwas sifted into a warm aqueous 30% solution of six mols of formaldehyde.A small amount of soda ash was added to bring the pH of the solutionbetween 6 and 7. The

of memuumWMQmd a dry of 340 lbs. per

70C.for15minutes. Amlxturewasprepared fromlpartsofthesoluti6nofthiscondensate.dopartsofwheatflounanddpartsofanaqueous 40% ammonium thiocyanatesolution. The resulting paste was spread on is" birchwood at 13gramspersquarefootofsurfaceandathreeplysheetformedinapressat200lbs.persquareinch and 220 F. for five minutes. The resulting panelwas highly satisfactory in water-resistance as shown by the boilingwater test. A ureaformaldehyde condensate mixed with flour and catalystin the same proportions as for the above 'blsthioammeline ether adhesivewas similarly applied to 1%" birchwoodveneer. At the time when theselatter panels were completely delaminated by boiling water, the panelsbonded with.

m. adding 3.25 parts of calcium chloride. The temwas? square in 7' Anadhesive was prepsred'by neutralizing 243 parts of an aqueous 87%formaldehyde solution with lime until a pH of 7.2 was reached, heatingthe neutralized solution to 85 C., stirring. in 178 parts of powderedbisthioammeline diethyl ether over a period of about tenminutes', andthen perature was maintained between 85 C. and 90 C. until a'criticalsolution temperature of 90 C. was reached; 1. e., 90' C. was the lowesttemperature at which the solution remained clear. The solution was thensubjected to vacuum and 140 parts ofwater was distilled off at pressuresthe bisthioammeline diethyl ether-formaldehyd were entirely intact.

Example 3 f 486 parts of, a 37% aqueous solution of formaldehyde washeated to 85 C. and 358 parts of powdered p,p'-bisthioammeline diethylether added with good stirring. The mixture was. maintained at 85 C.until the thioarnmeline ether was completely dissolved. The pH of the .7

resulting mixture was then adjusted to a value between 6 and 7 byadditions of small amounts of soda ash solution and formic acid. Thesolution was then strained to remove any insoluble material and allowedto cool. Crystals separated,- were broken up, washed with water,filtered oil, and dried at about 40 C. This solid material correspondsapproximately to the hexamethylol derivative and may be obtained inyields as high as 95% of theory.

100 parts of this methylol product, 100 parts of wheat flour, 2.5 partsof ammonium thiccyanate, and 100 parts of a solvent composed of halfwater and half ethanol were made into an adhesive paste. The adhesivewas spread on birchwood at the rate of 0.03 lb. per square foot.Three-ply veneers were formed in a press at 200 lbs. per square inch and240 F. for five minutes. The resulting plywood had a shear strength of320 lbs. per square inch.

Example 4 and 60 C. The water was replaced with ethyl alcohol in orderto maintain a. stable solution. The final solution, constituting 750parts, had a solids content of 56% and a pH of 7.6.

There was added to 100 parts of the above solution 8 parts of a 25%alcoholic ammonium thiocyanate solution. This mixture was spread onbirch veneer at 0.03 lb. per square foot and the laminae formed into athree-ply panel after a four minute treatmentinapress at 200 lbs. persquare inch and 240 F. The

had a dry shear strength of 350 lbs. per square" inch. Samples of theplywood were boiled in water for three hours without delamination andbetween 100, and 20 mm. The residual mass was a thick paste which wastaken up in 127 parts of ethyl alcohol to yield a homogeneous viscoussolution of 66.7% solids and a viscosity of Z on the Gardner-Holdtscale.

In place of lime in the above example there may be used sodium hydroxideor soda ash with entirely satisfactory results, or the solution may betreated with activated charcoal. In place of the calcium chloride theremay be used zinc chloride, magnesium chloride, or barium chloride.likewise with satisfactory results. The above resinous solution may befurther modifie with extenders, thickeners, etc.

To the viscous solution as prepared above there was added about 4% of anaqueous 40% solution of ammonium thiocyanate. The resulting solution wasspread on' birch sheets at 12 mm. per square foot and three-plyveneers-formed at 200 lbs. per square inch pressure, 280 F., and presstimes of two to four minutes. The shear strength of the resulting panelsvaried from 300 to 500 lbs. per square inch. Samples subjected toboiling .water for thirty minutes still exhibited shear strengths of atleast 275 lbs. per square inch.

' Example 6 195 parts of an aqueous 37% formaldehyde solution was heatedin a reactor equipped with a reflux condenser to 80 C. and 35.6 partsof. powdered ofl-bisthioammeline diethyl ether and 54 parts of urea.added with stirring. When solution was. complete, the mixture was cooledto 60 C. and the pH adjusted between 6 and 7 with a little 10% aqueoussoda ash solution. The

temperature was .then raised to 85-90 C. and maintained at this pointuntil a viscosity between 75 seconds and 150 seconds, as measured at 25C. in a Universal Saybolt viscosimeter, was reached. The temperature wasthen lowered to 50-80" C. and water removed under low pressure. when 80to 110 parts of water had been removed, a viscous product was obtainedwhich was highly satisfactory as a plywood adhesive. Upon addition of asmall amount of an acid salt, an ammonium salt, or a mixture ofacid-type catalyst and ammonia, the solution was ready for application.

In place of the urea used above, there may be added thiourea; in wholeor in part, or other open-chain carbamide, such as urethane, formamide,acetamide, or alkyl or phenyl substituted urea. Also small amounts ofcalicum chloride,

zinc chloride, magnesium chloride, etc. maybe.

used in the reacting mixture.

The above condensates were combined with --thickening agents, extenders,or blood to give highly useful adhesives. A mixture of parts of theabove condensate, 67 parts of water, 70

parts of wheat or rye flour, and 3 parts of ammonium sulfatewas-thoroughly stirred until a ammonium thiocyanate. Initial shear strenth of three-ply birch panels bonded with this mixture was higher thanthe strength of panels bonded with a similar mixture without blood.

Likewise, the panels bonded with the mix containing blood withstood morecycles of alternate wetting and drying, being intact after fifteencycles, whereas without blood in the mixture fail.-

ures began at about 10 cycles. Blood acts, therefore, not only as athickener butalso as a binding agent in conJunction with thebisthioammeline ether-formaldehyde condensates.

Example 7 An adhesive composition was prepared from 195 parts of aqueous37% formaldehyde solution, 40 parts of bis(thioammelinoethoxy) ethylene,obtained by reacting two molecular proportions of thioammeline and oneof dichlorotriethylene glycol. and 54 parts of urea by following theprocedure described in Example 6. The viscous solution, treated withacid-type catalyst provides a useful composition for binding cork inbottle caps, or in forming plywood. This condensate may likewise bemixed with thickening agents or blood. a

The co-condensates of a bisthioammeline ether, an open chaincarbamide,-and formaldehyde are soluble and stable with little or noalcohol. This is advantageous when it is desired to use blood in themixture, as too high concentrations of alcohol make it somewhatdifllcult to use blood.

-We claim:

1. An adhesivecomprising a solution of a condensate of a bisthioammelineether and formaldehyde, an acidic condensation catalyst for hardeningsaid condensate, and soluble blood.

2. An adhesive comprising a solution of a condensate of abisthioammeline ether and formaldehyde, an acidic condensation catalystfor hardening said condensate, soluble blood, and a thickening agent.

3. An adhesive comprising a solution of a condensate of abisthioammeline ether and formaldehyde. an acidic condensation catalyst.soluble blood, and a cereal grain flour.

4. An adhesive comprising a solution of a fl,fl'-bisthioammeline diethylether-formaldehyde condensates, acidic condensation catalyst forhardening said condemate, soluble blood, and wheat flour.

5. An adhesive comprising a solution of a condensate offl,fl'-bisthioammeline diethyl ether, urea, and formaldehyde, anammonium salt, soluble blood. and a cereal grain flour.

6. An adhesive comprising a solution of a condensate of ar-bisthioammeline diethyl ether, urea, formaldehyde, and an alkalineearth halide, an acidic condensation catalyst for hardenin saidcondensate, soluble blood, and a cereal grain flour.

7. The process of bonding materials which comprises applying toobjects'to be bonded a solution containing a condensate ofp,p'-bisthioammeline diethyl ether, another methylol-forming compound,and formaldehyde, soluble blood, and an ammonium salt, and pressing theobjects together atot emperatures between about 200 F. and about 35 I".

8. The process of bonding materials which comprises applying to objectsto be bonded a solution containing a condensate of SW-bisthioammelinediethyl ether, an open-chain carbamide capable of forming a methylolderivative, and formaldehyde, soluble blood, and an ammonium salt andpressing the objects together at temperatures between about 200 F. and350 F.

9. The process of bonding materials which comprises applying to objectsto be bonded a solution containing a condensate offi,fi'-bisthioammeline diethyl ether, urea, and formaldehyde, solubleblood, and an ammonium salt, and pressing the objects together attemperatures between about 200 F. and about 350 F.

10. The process of bonding plywood which comprises coating at least onesurface of wood veneers with a solution containing a condensate of{LE-bisthioammeline diethyl ether, urea, and formaldehyde, solubleblood, a cereal grain flour, an ammonium salt, and ammonia and pressingsaid coated veneers together at temperatures between about 200 F. and350 F.

11. In a muiti-ply structure wherein at least two wood laminae arebonded together, the improvement which resides in the bonding togetherof said laminae with an adhesive comprising a hardened bisthioammelinepolyalkylen etherformaldehyde condensate and blood.

HERMAN A. BRUSON. JAMES L. RAmEY.

